1. Field of the Invention
The present invention relates to a method of producing a p-type nitride based III-V compound semiconductor, which is intended to activate a p-type impurity by applying an electric field to the semiconductor, and a method of fabricating a semiconductor device using the semiconductor.
2. Description of the Related Art
A nitride based III-V compound semiconductor, such as GaN, AlGaN compound crystal, and AlInGaN compound crystal have been used as base materials for light emitting devices allowing light emission in a range from a visual region to an ultraviolet region, or as base materials for electronic devices. In particular, a light emitting diode (LED) using a nitride based III-V compound semiconductor has become commercially practical and a focus of attention. Further, a semiconductor laser (LD) using a nitride based III-V compound semiconductor has been reported as a useful laser and has been used particularly as a light source of optical disk drives.
From the practical viewpoint of devices such as LEDs and LDs, it is important to produce a nitride based III-V compound semiconductor having a quality being high enough to be usable as a base material of the devices. In particular, to fabricate optical devices allowing effective current-carrying, it has been required to produce p-type and n-type nitride based III-V compound semiconductors having high qualities.
A nitride based III-V compound semiconductor is generally produced by epitaxial growth of the semiconductor on a substrate by a MOCVD (Metal Organic Chemical Vapor Deposition) process or the like. In this case, an n-type nitride based III-V compound semiconductor having a high quality can be easily produced by epitaxial growth with the addition of an n-type impurity such as silicon (Si). On the contrary, a p-type nitride based III-V compound semiconductor having a high quality cannot be produced only by epitaxial growth with the addition of a p-type impurity such as magnesium (Mg), and to enhance the quality of such a p-type semiconductor, the p-type impurity is required to be activated.
Methods of activating a p-type impurity have been variously proposed. For example, Japanese Patent No. 2540791 has disclosed a method of activating a p-type impurity by growing a nitride based III-V compound semiconductor by the MOCVD process, and annealing the semiconductor in an atmosphere substantially not containing hydrogen at a temperature of 400xc2x0 C. or more; and Japanese Patent Laid-open No. Hei 9-162442 has disclosed a method of activating a p-type impurity by forming a pn-junction or pin-junction, and forming an electrostatic field across the junction.
The method disclosed in Japanese Patent No. 2540791, however, has the problems that since the atmosphere at the time of heating is limited, the degree of freedom of production is low, and that since the annealing must be performed at a high temperature of 600xc2x0 C. or more for 10 to 20 min in order to activate the p-type impurity sufficiently from the practical viewpoint, nitrogen may be released from the nitride based III-V compound semiconductor during the annealing, and therefore, a protective film for preventing the release of nitrogen must be formed. According to this method, there occurs a further problem that, in the step of fabricating a light emitting device in which laser annealing is performed for activation of a p-type impurity, since the p-type semiconductor is left in a high temperature state for 10 to 20 min, elements of an active layer are diffused to collapse the steepness of a superlattice structure or the p-type impurity in the p-type semiconductor is diffused to enter the active layer, thereby deteriorating the light emission characteristic. The method disclosed in Japanese Patent Laid-open No. Hei 9-162442 has a problem that since electrodes must be formed on both the p-side and n-side for forming an electrostatic field across the pn-junction or pin-junction, such a method is unstable for mass-production.
An object of the present invention is to provide a method of producing a p-type nitride based III-V compound semiconductor, which is capable of simply activating a p-type impurity, and a method of fabricating a semiconductor device using the compound semiconductor thus produced.
To achieve the above object, according to an aspect of the present invention, there is provided a method of producing a p-type nitride based III-V compound semiconductor, including the steps of: preparing a nitride based III-V compound semiconductor containing at least one kind selected from group IIIB elements, at least nitrogen selected from group VB elements, and a p-type impurity; and applying a radio frequency field to the nitride based III-V compound semiconductor thus prepared.
According to another aspect of the present invention, there is provided a method of fabricating a semiconductor device, including the step of: forming a p-type nitride based III-V compound semiconductor by preparing a nitride based III-V compound semiconductor containing at least one kind selected from group IIIB elements, at least nitrogen selected from group VB elements, and a p-type impurity, and applying a radio frequency field to the nitride based III-V compound semiconductor thus prepared.
In the method of producing a p-type nitride based III-V compound semiconductor according to the present invention and a method of fabricating a semiconductor device according to the present invention, since a p-type impurity is activated by applying a radio frequency field, the carrier density can be increased.